Agricultural implements such as cultivators, seeders, and the like commonly comprise a frame configured to extend laterally from a central hitch where a tractor is connected for towing the implement. The frame typically comprises a lateral beam extending generally perpendicular to the path of the implement, and a fore and aft beam extending generally in alignment with the implement path, as for example in the implement generally illustrated in U.S. Pat. No. 5,113,956 to Friesen et al. In the implement of Friesen et at. the implement frame comprises a single lateral beam extending to each of the right and left sides of the implement, and a single fore and aft beam to which the inner ends of the right and left lateral beams are attached. The hitch for attachment of the tractor to tow the implement is on the front end of the fore and aft beam.
It is desired in many implements to have several rows of ground engaging tools extending laterally from the implement path along the frame in order that a rear tool follows a path that is offset from the path of a leading tool. A plurality of lateral beams is spaced from the front of the implement to the rear thereof, and the lateral beams are connected by fore and aft beams extending generally in alignment with the implement path, as illustrated for example in U.S. Pat. No. 6,684,962 to Lewallen and U.S. Pat. No. 4,683,957 to Bussiere.
The lateral and fore and aft beams are welded or bolted together to form a rigid structure that will have sufficient structural strength to resist deforming when the ground engaging tools are engaged in the ground. The hitch is typically attached to the middle of the frame where inner ends of the lateral beams are attached to fore and aft beams. The lateral beams extend laterally outward, to outer ends located on each side. The width of such implements varies considerably, and modern implement are commonly 60 feet wide or more.
As the frame moves forward towed by the tractor, the hitch exerts the required force on inner ends of the lateral beams to move the tools through the ground. The tools resist the movement and thus exert a rearward force on the lateral beams of the frame. The tools on the outer ends of the frame exert a considerable bending force on the lateral beams relative to the inner ends of the frame, where the force to move the frame forward is exerted. Up to a point the beams can be made strong enough to resist this bending force, and outer ends of the lateral beams will flex rearward in response to shock forces such as when the implement strikes a rock, root, or like obstruction. The lateral beams thus act like a shock absorber to limit the peak forces on the frame, wing hinges, hitch, and the like.
While such flexing is beneficial, excessive flexing leads to accelerated metal fatigue and eventually to frame failure. Particularly in wider implements where the forces exerted on the outer end of the frame during operation can be large it is required to provide diagonal braces. The brace can be a cable or beam extending generally from a front inner portion of a frame section to an outside rear portion of the frame section, such that a rearward force on the outer end of the frame section puts the brace in tension. Similarly the brace can be a rigid beam extending generally from a rear inner portion of a frame section to an outside front portion of the frame section, such that a rearward force on the outer end of the frame section puts the beam in compression. The flexing rearward movement of the outside end of the frame section is thus resisted by the brace tied to the inner portion, nearer the inner ends of the lateral beams where the force is exerted by the towing tractor
Such diagonal braces render the frame section diagonally rigid. Metal fatigue is reduced, but the frame section can no longer flex to absorb shock loads, and peak forces on the frame, wing hinges, and hitch increase, and peak forces on the diagonal brace can be very high. Thus considerable reinforcement of the frame members is required to resist the higher shock forces on the frame.
A typical implement frame structure with braces in both tension and compression is generally illustrated in U.S. Pat. No. 6,684,962 to Lewallen.